1. Field of the Invention
The present invention relates to valves, and more particularly to a pressurizable valve for use in controlling the flow of crushed or powdered material in a lock hopper system and the like; and to a method of preventing, or reducing to a minimum, leakage between, and wear and abrasion of the stationary seating and movable parts of the valve.
2. The Prior Art
Valves for use in lock hopper systems handling crushed or powdered abrasive material such as coal, shale, dolomite, etc. are not new per se. However, most prior valves intended for such use are short-lived because the abrasive materials being handled are not effectively prevented from getting between the valve seat and the valve closure means, resulting in scoring, galling and abnormally rapid wear. Such prior valves also have the objection that abrasive material gets into the seals between the inlet and the outlet of the valve and between the pressure source and the atmosphere, which is conducive to further leakage and aggravates the need for frequent servicing.